Aircraft main engines not only provide propulsion for the aircraft, but in many instances may also be used to drive various other rotating components such as, for example, generators, compressors, and pumps, to thereby supply electrical, pneumatic, and/or hydraulic power. Generally, a gas turbine engine includes a combustor, a power turbine, and a compressor. During operation of the engine, the compressor draws in ambient air, compresses it, and supplies compressed air to the combustor. The compressor also typically includes a diffuser that diffuses the compressed air before it is supplied to the combustor. The combustor receives fuel from a fuel source and the compressed air from the compressor, and supplies high energy compressed air to the power turbine, causing it to rotate. The power turbine includes a shaft that may be used to drive the compressor.
Gas turbine engines generally take the form of an axial compressor or a centrifugal compressor, or some combination of both (i.e., an axial-centrifugal compressor). In an axial compressor, the flow of air through the compressor is at least substantially parallel to the axis of rotation. In a centrifugal compressor, the flow of air through the compressor is turned at least substantially perpendicular to the axis of rotation. An axial-centrifugal compressor includes an axial section (in which the flow of air through the compressor is at least substantially parallel to the axis of rotation) and a centrifugal section (in which the flow of air through the compressor is turned at least substantially perpendicular to the axis of rotation).
As mentioned above, compressors often include a diffuser to reduce the velocity of the air traveling from the compressor to the combustor, for example in a gas turbine engine with a through flow combustor. In addition, certain centrifugal compressors have both a first diffuser located relatively early in the compressor flow passage away from the combustor and a second diffuser (often called a pre-diffuser) located later in the flow passage proximate the combustor. However, to date, it has been difficult to implement such additional diffusers, or pre-diffusers, in connection with centrifugal compressors. Specifically, it has been difficult to implement such an additional diffuser in close proximity to the combustor of the gas turbine engine, because there generally needs to be significant space between the additional diffuser and the combustor to allow for the insertion and removal of fuel injectors from and to the combustor, for example for servicing. As a result, any placement of such a pre-diffuser in a centrifugal compressor would generally result in an undesirable increase in the length and/or weight of the engine.
Accordingly, there is a need for an improved diffuser system for a compressor, such as a centrifugal compressor, for example that potentially reduces pressure loss, or dump loss. There is also a need for a compressor, such as a centrifugal compressor, with an improved diffuser system, for example that potentially reduces pressure loss, or dump loss. There is a further need for a gas turbine engine with a compressor, such as a centrifugal compressor, with an improved diffuser system, for example that potentially reduces pressure loss, or dump loss. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.